1. Field of the Invention
The invention relates to a method and apparatus for measuring the position of a ferrule of a laser module, particularly to a method and apparatus for measuring the position of a ferrule of a laser module for compensating the shift of the ferrule after the laser module is welded.
2. Description of the Related Art
There are many types of laser module packaging, and the co-axial type and the box type are broadly used. The greatest challenge for the co-axial type of laser module packaging is to use a reliable and accurate jointing process. During the welding process, the rapid solidification of the welded region and the associated material shrinkage often cause a postweld shift (PWS) between the welded components. For a typical single-mode-fiber application, if the PWS-induced fiber alignment shift by the laser-welding-jointing process is even only a few micrometers, up to 50% or greater loss in the couple power may occur. During the solidification, shrinkage causes many different levels of shift, and there are many factors affecting the shift, such as the input welding energy, the joint geometric design and material's conditions. Since the solidification- shrinkage-induced PWS is a nonlinear behavior, it is a difficult task to analyze the PWS.
For the present laser module packaging, there is still not a quantitative measurement or a compensation principle for welded shift. In a conventional skill, it is measured by using hands to estimate the direction and level of the PWS. However, the sensitivity of the PWS for a coupled efficiency is smaller than 1 μm, and thus the measurement by using hands is not a quantitative measurement and is not accurately estimated, so that the additional welding process is inefficient, and the efficiency and yield of laser module packaging cannot be effectively improved.
Consequently, there is an existing need for a method and apparatus for measuring the position of a ferrule of a laser module.